[jira] [Commented] (AIRFLOW-111) DAG concurrency is not honored

["Shenghu Yang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AIRFLOW-111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15319568#comment-15319568 ] 

Shenghu Yang commented on AIRFLOW-111:
--------------------------------------

I think the bug is here:
https://github.com/apache/incubator-airflow/blob/18009d03311a0b29e14811865e0b13b19427b5e4/airflow/models.py#L1233-L1247

Let's see one task is already been 'QUEUED', and next time when we hit the above code, it will NOT check the 'self.task.dag.concurrency_reached', hence it will run the task beyond dag's concurrency.

One fix would be right after the above code, we add the following:
########################
if self.task.dag.concurrency_reached:
    logging.info("dag concurrency reached")
    return
########################

> DAG concurrency is not honored
> ------------------------------
>
>                 Key: AIRFLOW-111
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-111
>             Project: Apache Airflow
>          Issue Type: Sub-task
>          Components: celery, scheduler
>    Affects Versions: Airflow 1.6.2, Airflow 1.7.1.2
>         Environment: Version of Airflow: 1.6.2
> Airflow configuration: Running a Scheduler with LocalExecutor
> Operating System: 3.13.0-74-generic #118-Ubuntu SMP Thu Dec 17 22:52:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
> Python Version: 2.7.6
> Screen shots of your DAG's status:
>            Reporter: Shenghu Yang
>             Fix For: Airflow 2.0
>
>
> Description of Issue
> In our dag, we set the dag_args['concurrency'] = 8, however, when the scheduler starts to run, we can see this concurrency is not being honored, airflow scheduler will run up to num of the 'parallelism' (we set as 25) jobs.
> What did you expect to happen?
> dag_args['concurrency'] = 8 is honored, e.g. only run at most 8 jobs concurrently.
> What happened instead?
> when the dag starts to run, we can see the concurrency is not being honored, airflow scheduler/celery worker will run up to the 'parallelism' (we set as 25) jobs.
> Here is how you can reproduce this issue on your machine:
> create a dag which contains nothing but 25 parallelized jobs.
> set the dag dag_args['concurrency'] = 8
> set the airflow parallelism to 25
> then run: airflow scheduler
> you will see all 25 jobs are scheduled to run, not 8.



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